A “quarter” system is commonly used in the hardwood lumber industry when referring to thickness. 4/4 refers to a 1 inch thick board, 6/4 is 1-1/2 inch, 8/4 is 2 inches, and so on.

Quarter Size

Rough Dimension

S1S

S2S

4/4

1″

15/16″

7/8″

6/4

1 1/2′

1 – 7/16″

1 – 3/8″

8/4

2″

1-15/16″

1-13/16″

12/4

3″

2-13/16″

2-3/4″

Lumber Grading

Most of the hardwood lumber in the United States and Canada is graded according to the rules established by the National Hardwood Lumber Association (NHLA). In fact, the NHLA grading rules form the basis for much of the international hardwood lumber trade. The standard grades of hardwood lumber as defined by the NHLA (in descending order of quality) are FAS, FAS 1-Face (F1F), Selects, No. 1 Common, No. 2A Common, No. 2B Common, Sound Wormy, No. 3A Common, and No. 3B Common. In practice, some of the above grades are rarely used in the commercial trade and others are typically combined. For example, FAS and FAS 1-Face are usually combined and sold as “Face And Better”, FAS and Selects as “Sel and Better”, No. 1 Common and Selects as “No. 1 Common and Better”, and No. 2A Common and 2B Common as “No. 2 Common”. The grade of Sound Wormy is rarely used commercially.

Grading is based on the size and number of clear cuttings that can be obtained from a board when it is cut up and used for furniture or other products. The higher grades require wider and longer cuttings of clear wood than the lower grades. The specified clear face yield is also realized in a smaller number of cuttings with the higher grades. In the lower grades, the larger number of cuttings permitted provide more leeway in cutting between defects to realize the yield. With a few exceptions, grade is determined from the worst side of a board.

The surface measure of a board is used to determine the number of cuttings permitted for a given grade. For example, the FAS grade specifies a minimum size of 4″ x 5′ or 3″ x 7′ for cuttings taken from a board that is at least 6″ wide and 8′ long. The maximum number of cuttings is nominally four to produce a clear-face yield of 83 1/3 percent. If the surface area of the board is greater than 6 square feet, an additional cutting is allowed if the yield can be raised to 91 2/3 percent.

In selecting wood for a woodworking project, consider the size of the boards required. In many situations, lower grades are a more economical choice than the higher grades; in particular, consider using Select or No 1. Common grade boards rather than FAS if a relatively larger number of small, clear pieces are required.

Note that unlike softwood grades, hardwood grades do not indicate the strength of the board. Another difference is hardwood grading does not require a certified or licensed grader. Purchasing lumber from well-established reputable sources increases your chances of consistently obtaining accurately graded lumber.

The standard hardwood lumber grades are summarized below:

Grade

Minimum board length

Minimum board width

Minimum cutting size

Min. area of clear cuttings required

FAS

8′

6″

4″ x 5′
3″ x 7′

83-1/3%

F1F

8′

6″

4″ x 5′
3″ x 7′

83-1/3%

4″ x 2′
3″ x 3′

66-2/3%

Selects

6′

4″

4″ x 5′
3″ x 7

83-1/3%, 66-2/3%

No. 1C

4′

3″

4″ x 2′
3″ x 3′

66-2/3%

No. 2AC

4′

3″

3″ x 2′

50%

No. 2BC

4′

3″

3″ x 2′

50%

No. 3AC

4′

3″

3″ x 2′

33-1/3%

No. 3BC

4′

3″

1-1/2″ x 2′

25%

FAS
FAS derives from an earlier grade known as “First and Seconds”. It is the best and most expensive grade. Boards 6″ and wider, 8′ and longer. Yields 83-1/3 percent of clear face cuttings with minimum sizes of 4″ x 5′, or 3″ x 7′. Suitable for fine furniture, interior joinery, solid wood moldings, and other applications where clear, wide boards are needed.

FAS 1-Face (F1F)
One face meets FAS requirements and the poorer face meets Number 1 Common grade requirements. Usually combined with FAS lumber, thereby providing at least one FAS face.

Selects
Face side is FAS, back side is No. 1 Common. Boards are 4″ and wider, 6′ and longer. Yields 83-1/3 percent clear face cuttings with minimum sizes of 4″ x 5′, or 3″ x 7′. A cost effective substitute for FAS when only one good face is required.

No. 1 Common
Often referred to as “Cabinet” grade in the USA due to its extensive use for kitchen cabinets. Boards are 3″ and wider, 4′ and longer. Yields 66-2/3 percent clear face cuttings with minimum sizes of 4″ x 2′, or 3″ x 3′. Provides good value, especially if relatively small pieces can be used.

No. 2A CommonAlso known as “Economy” grade. Boards are 3″ and wider, 4′ and longer. Yields 50 percent clear face cuttings 3″ and wider by 2′ and longer. Grade of choice for US hardwood flooring industry.

No. 2B Common
Same as No. 2A Common, except that stain and other sound defects are admitted in the clear cuttings. An excellent paint grade.

Sound Wormy
Same requirements as #1 Common and better but wormholes, limited sound knots and other imperfections allowed. Not commonly available.